Thermoformable Web Splicer and Method

ABSTRACT

An apparatus and method are provided for splicing together old and new thermoformable sheets in order to supply a continuous thermoforming operation. The method for joining together thermoformable sheets includes: providing a first thermoformable sheet with a trailing edge and a second thermoformable sheet with a leading edge; forming a terminal edge portion with a hot element along the trailing edge and a complementary terminal edge portion along the leading edge by severing a scrap sheet from each portion; laterally retracting each scrap portion away from the trailing edge and the leading edge; and joining together the first thermoformable sheet and the second thermoformable sheet by interlocking together the terminal edge portion with the complementary terminal edge portion.

RELATED PATENT DATA

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/218,979 which was filed Jun. 21, 2009, entitled “Hot WireSplicer”, the entirety of which is incorporated by reference herein.

TECHNICAL FIELD

This invention pertains to apparatus and methods for splicing togetherfilms or sheets of thermoplastic material. More particularly, thepresent invention relates to butt welding of thermoplastic sheet stockmaterial with a splice to continuously deliver sheet material to athermoforming process.

BACKGROUND OF THE INVENTION

Apparatus and methods are known for joining together sheets ofthermoplastic film being used to feed a thermoforming apparatus. Tapingsplicing apparatus are known. Attempts have been made to butt weldthermoplastic sheets and films in an effort to continuously supply sheetto a thermoforming apparatus. However, no one has been successful inperfecting a process that is continuous and does not interrupt operationof the thermoforming apparatus. For example, U.S. Pat. Nos. 3,769,124;3,834,971; 3,956,047; and 4,001,067 illustrate one attempt to splicesheets of thermoplastic film, but a lack of commercial success resulteddue to shortcomings.

SUMMARY OF THE INVENTION

A splicing apparatus and method are provided for butt welding orsplicing together a trailing end of a thermoplastic sheet of stockmaterial with a leading end of a thermoplastic sheet of stock materialto impart a continuous supply of sheet. A pair of clamps are used tomanipulate and position the overlapped sheets while a hot wire ismanipulated to sever the sheets and weld together the heated ends of thesheets, thereby joining them together into a continuous sheet.

According to one aspect, a method is provided for joining togetherthermoformable sheets. The method includes: providing a firstthermoformable sheet overlapped with a second thermoformable sheet;moving a heating element through the first sheet and the second sheet toform a trailing terminal edge and a leading terminal edge, respectively;aligning in proximate, spaced-apart relation the trailing terminal edgeand the leading terminal edge; inserting the heating element between andspaced from the trailing terminal edge and the leading terminal edge;while holding the heating element between the trailing terminal edge andthe leading terminal edge, heating the trailing terminal edge and theleading terminal edge with the heating element sufficiently to impartmelt-back of each edge away from the heating element at a melt-backrate; while heating the leading terminal edge and the trailing terminaledge, moving the leading terminal edge and the trailing terminal edgeeach towards the heating element at a rate no greater than the melt-backrate so as to prevent contact of each edge with the heating elementwhile maintaining proximity with the heating element to deliver heat toeach edge; removing the heating element from between the trailingterminal edge and the leading terminal edge; and after removing, fusingtogether the leading terminal edge and the trailing terminal edge bymoving together the leading terminal edge and the trailing terminal edgeuntil respective melted portions on each edge engage.

According to another aspect, a method is provided for joining togetherthermoformable sheets. The method includes providing a firstthermoformable sheet with a trailing terminal edge and a secondthermoformable sheet with a leading terminal edge; aligning inproximate, spaced-apart relation the trailing terminal edge and theleading terminal edge; inserting a heating element between and spacedfrom the trailing terminal edge and the leading terminal edge; whileholding the heating element between the trailing terminal edge and theleading terminal edge, heating the trailing terminal edge and theleading terminal edge with the heating element sufficiently to impartmelt-back of each edge away from the heating element at a melt-backrate; while heating the leading terminal edge and the trailing terminaledge, moving the leading terminal edge and the trailing terminal edgeeach towards the heating element at a rate no greater than the melt-backrate so as to prevent contact of each edge with the heating elementwhile maintaining proximity with the heating element to deliver heat toeach edge; removing the heating element from between the trailingterminal edge and the leading terminal edge; and after removing, movingthe leading terminal edge and the trailing terminal edge together untilrespective melted portions on each edge engage.

According to yet another aspect, an apparatus is provided for joiningtogether thermoformable sheets. The apparatus includes a frame, anentrance vacuum clamping bar assembly, an exit vacuum clamping barassembly, a sheet severing mechanism, and at least one sheet actuator.The entrance vacuum clamping bar assembly is supported by the frame andhas a vacuum clamping member supported for movement toward and away fora vacuum servo member generally perpendicular to a sheet travel path.The vacuum clamping member is further supported for retraction andextension parallel to the sheet travel path. The exit vacuum clampingbar assembly is supported by the frame downstream of the entrance vacuumclamping bar assembly and has a clamping member supported for movementtoward and away from a vacuum servo member generally perpendicular to asheet travel path. The vacuum clamping member is further supported forretraction and extension parallel to the sheet travel path. The sheetsevering mechanism is provided for severing an overlapped old sheet andnew sheet. The at least one actuator is carried by the frame and isconfigured to move each of the vacuum clamping members toward and awayfrom a splice to retract scrap sheet away from a splice line between theentrance vacuum clamping bar assembly and the exit vacuum clamping barassembly. One of the entrance and exit vacuum clamping member isprovided above the respective vacuum servo member and another of theentrance and exit vacuum clamping member is provided below therespective vacuum servo member.

These and other aspects of the present invention will be described ingreater detail hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a perspective view from above of a web splicing apparatusincluding a downstream web accumulator shown in a lowered position.

FIG. 2 is a perspective view of the web splicing apparatus of claim 1and showing the web accumulator shown in raised position.

FIG. 3 is a simplified elevational view of the web splicing apparatus ofFIGS. 1-2 showing the web accumulator in a lowered and raised position,including a block diagram of control system and drive components alongwith a simplified perspective view of a web payout.

FIG. 4 is a simplified plan view of a web splicing apparatus.

FIG. 5 is a simplified right elevational view of the web splicingapparatus of FIG. 1 from the downstream end.

FIG. 6 is a simplified vertical sectional view taken along line 6-6 ofFIG. 4.

FIG. 7 is a simplified partial and vertical sectional view taken in anopposite direction of the view in FIG. 6 of the pre-feed section for theweb splicing apparatus of FIGS. 1-6.

FIG. 8 is a simplified partial and vertical side view of the splicesection assembly for the web splicing apparatus of FIGS. 1-6.

FIG. 9 is a simplified component view of the servo bars and clamp barsof the splice section of FIG. 8.

FIG. 10 is a vertical sectional view of selected splicer sectioncomponents corresponding with a sheet payout mode.

FIG. 11 is an enlarged view taken from the encircled region 11 of FIG.10.

FIG. 12 is a vertical sectional view of selected splicer sectioncomponents corresponding with a new sheet delivery mode.

FIG. 13 is an enlarged view taken from the encircled region 13 of FIG.12.

FIG. 14 is a vertical sectional view of selected splicer sectioncomponents corresponding with a vacuum clamp mode.

FIG. 15 is an enlarged view taken from the encircled region 15 of FIG.14.

FIG. 16 is a vertical sectional view of selected splicer sectioncomponents corresponding with a sheet apart mode.

FIG. 17 is an enlarged view taken from the encircled region 17 of FIG.16.

FIG. 18 is a vertical sectional view of selected splicer sectioncomponents corresponding with a wire cut sheets mode.

FIG. 19 is an enlarged view taken from the encircled region 19 of FIG.18.

FIG. 20 is a vertical sectional view of selected splicer sectioncomponents corresponding with a scrap retract mode.

FIG. 21 is an enlarged view taken from the encircled region 21 of FIG.20.

FIG. 22 is a vertical sectional view of selected splicer sectioncomponents corresponding with an alignment mode.

FIG. 23 is an enlarged view taken from the encircled region 23 of FIG.22.

FIG. 23A is a further enlarged view taken from the encircled region 23Aof FIG. 23.

FIG. 24 is a vertical sectional view of selected splicer sectioncomponents corresponding with a sheet approach mode.

FIG. 25 is an enlarged view taken from the encircled region 25 of FIG.24.

FIG. 25A is a further enlarged view taken from the encircled region 25Aof FIG. 25.

FIG. 25B is further enlarged view taken from the encircled region 25 ofFIG. 25, but taken later in time than FIG. 25A.

FIG. 26 is a vertical sectional view of selected splicer sectioncomponents corresponding with a wire withdraw and sheet load mode.

FIG. 27 is an enlarged view taken from the encircled region 27 of FIG.26.

FIG. 27A is a further enlarged view taken from the encircled region 27Aof FIG. 27.

FIG. 27B is a further enlarged view taken from the encircled region 27Aof FIG. 27, but taken later in time than FIG. 27A.

FIG. 28 is a vertical sectional view of selected splicer sectioncomponents corresponding with a sheet apart and scrap withdrawal mode.

FIG. 29 is an enlarged view taken from the encircled region 29 of FIG.28.

FIG. 30 is an enlarged component perspective view of an entrance vacuumbar assembly of FIGS. 6 and 9.

FIG. 31 is an enlarged component perspective view of an exit vacuum barassembly of FIGS. 6 and 9.

FIG. 32 is a component perspective view of the splice section assemblyof FIG. 8 taken from the same end of the machine, but omitting the hotwire web cutting mechanism to simplify the drawing.

FIG. 33 is a component perspective view of the splice section assemblyof FIGS. 8 and 30 taken from an opposite end of the machine.

FIG. 34 is a component perspective view of the splice alignment assemblymechanism taken from the same end as FIG. 33.

FIG. 35 is a component perspective view of the splice tilt mechanismtaken from the same end as FIG. 33.

FIG. 36 is a component perspective view of an assembly for the hot wireweb cutting mechanism.

FIG. 37 is a process flow diagram assembled together from FIGS. 37A and37B and showing the logic processing for accumulating surplus web neededby a thermoforming machine during a web splicing operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

Reference will now be made to one embodiment of Applicants' inventionfor a thermoforming sheet splicing apparatus and method for joiningtogether old and new thermoformable plastic sheets of material forcontinuously feeding a thermoforming press when molding articles. Whilethe invention is described by way of one embodiment, it is understoodthat the description is not intended to limit the invention to suchembodiment, but is intended to cover alternatives, equivalents, andmodifications which may be broader than the embodiment, but which areincluded within the scope of the appended claims.

In an effort to prevent obscuring the invention at hand, only detailsgermane to implementing the invention will be described in great detail,with presently understood peripheral details being omitted, as needed,as being presently understood in the art.

FIGS. 1-3 show a sheet or web splicing apparatus 10 according to thepresent invention. As shown in FIGS. 1-3, apparatus 10 includes a webaccumulator 11 that is mounted atop a splicer frame 12. Web splicingapparatus 10 operates to splice a leading edge of a new web onto atrailing edge of an old web, each typically stored as a roll, in amanner that does not interrupt feeding of a thermoformable web into acontinuously operating thermoforming line. Web accumulator 11 has beenomitted from FIGS. 4-6 in order to simplify the drawings, but it isunderstood that accumulator 11 is normally provided atop apparatus 10 inFIGS. 4-6, according to one implementation. Optionally, accumulator 11can be omitted and another form of accumulation device can be used inconjunction with the remaining portion of apparatus 10. Alternatively,accumulator 11 can be omitted from apparatus 10 or can be provided as aseparate stand-along machine. Web accumulator 10 is raised in order tostore an extra length of thermoformable web sheet material during a websplicing operation so that delivery of the web to a downstreamthermoforming machine does not interrupt operation of the thermoformingmachine during a web splicing operation. The accumulated length is paidout during a splicing operation.

As shown in FIG. 1, web accumulator 11 provides a cylindrical supportroller 25 that is raised and lowered in order to temporarily store anextra length of thermoformable web to supply the web while a splicingoperation is being performed with apparatus 10, such that a downstreamthermoforming operation does not need to be slowed down or stoppedduring a splicing operation. A typical thermoforming operation iscontinuous, with a thermoformable web being delivered in a continuouslyfed, intermittent motion matching the motion of platens opening andclosing on a heated web such that the web is stopped during a formingstep and moved after the thermoforming step to prepare for a subsequentthermoforming step.

Web accumulator 11 includes a pair of support arms 27 and 29 that mountonto frame 12 of apparatus 10 with a plurality of threaded fasteners(not shown). A pair of curved tubular lift arms 31 and 33 is pivotallysupported at a top end of each support arm 27 and 29, respectively. Adistal end of each lift arm 31 and 33 supports one end of a cylindricalroller 25 for rotation. A web of thermoformable material that leavesexit assembly 18 passes over roller 25. By raising roller 25, an extralength of web can be stored atop roller 25 for later use while the webis being shuttled back and forth within splicing apparatus 10 whensplicing together a nearly depleted, or old web and a new web.

More particularly, roller 25 is raised and lowered by extending andretracting a pair of pneumatic cylinders 43 and 45 that mount betweensupport arms 27 and 29 and lift arms 31 and 33, respectively, with apivot pin at each end. Alternatively, a linear servo drive and motor,rack and pinion, ball screw, or other moving device can be used in placeof pneumatic cylinders 43 and 45 in order to raise and lower roller 25.FIG. 2 shows roller 25 in a raised configuration, whereas FIG. 1 showsroller 25 in a lowered configuration. A pair of cross bars 39 and 41,each of rectangular cross section, are connected between support arms 27and 29 with threaded fasteners to stiffen arms 31 and 33. Likewise, apair of cross bars 35 and 37 is connected between lift arms 31 and 33with clamp brackets 63, 69 and 65, 67, respectively. Bars 35 and 37 arefurther secured together where they cross using a spacer boss and athrough-bolt fastener.

According to one construction, roller 25 is formed from a cylindricalpiece of aluminum machined with a central bore and cylindrical endgrooves that each receive a standard deep groove roller ball bearing 51and 53, respectively. A central bolt shaft 75 extends through roller 25,as well as inner races of bearings 51 and 53, and bolts onto endmounting brackets 47 and 49 on arms 31 and 33, respectively.

Proximal ends of lift arms 31 and 33 are each pivotally supported bysupport arms 27 and 29 using cylindrical ball bearing assemblies 59 and61, respectively. A cylindrical stand-off shaft 55 and 57 is mountedonto each arm 27 and 29, respectively. An inner race of each bearingassembly 59 and 61 is mounted onto each stand-off shaft 55 and 57,respectively. Each lift arm 31 and 33 is constructed from a piece offormed steel conduit, with a proximal end being crimped together. Acylindrical bore is then formed in the crimped portion of each arm 31and 33, into which an outer race of each bearing assembly 59 and 61 isthen secured with a press-fit.

FIG. 2 illustrates accumulator 11 articulated to a position with roller25 raised in order to accumulate a web of thermoformable materialexiting exit assembly 18 of splicer 10. A web of thermoformable materialleaves splicer 10 via exit assembly 18 and passes over roller 25. Roller25 is raised and the web is fed at an increased rate prior to a splicingoperation in order to accumulate an extra length of web material overroller 25, which is later used to feed a thermoforming machinedownstream of splicer 10 during a splicing operation. During thesplicing operation, the accumulated web is used to feed a downstreamthermoforming machine. Roller 25 is lowered at a controlled rate inorder to supply the accumulated web during a splicing operation to thethermoforming machine, while preventing the web from collecting on afactory floor.

As shown in FIG. 3, a computer 73 having a user interface 19 enablessetup and operator control of a control system 13 (see FIG. 3) thatconfigures the height, timing and speed with which roller 25 is raisedprior to and during a web splicing operation using splicer 10.

FIG. 3 illustrates control system 13 in a simplified block diagram formfor controlling operation of splicer 10, including controlledarticulation of accumulator 11. Control system 13 is implemented oncomputer 73. Control system 13 includes processing circuitry 15, memory17, user interface 19 and a control algorithm 21.

Control algorithm 21 enables control system 13 to control delivery ofpneumatic fluid from a pneumatic source 77 via a pneumatic control valve23 and to control operation of servomotors 28, 30, 32, 34 and 36.According to one implementation, control algorithm 21 includes a recipecomprising control settings that can be set and retrieved to raiseroller 25 to a sufficient height and at an appropriate rate based uponoperating characteristics of a specific thermoforming line. For example,a specific thermoformable web material on a specific thermoforming linewill operate with a specific shot length and with a specific cycle time.This information is combined with a period of time needed to perform aweb splice, thereby enabling determination of how much web needs to beaccumulated in order to prevent any need to slow down or stop thethermoforming line.

In order to enable automatic operation of splicer 10 to perform a splicebetween a terminal portion of an old web roll and a leading portion of anew web roll, a sensing apparatus is implemented on a web roll payout 5.The sensing apparatus comprises an optical sensor 6 having an emitterand detector that combines with an aligned mirror 8 to provided anoptical line of sight 9 that generates a signal when an old web roll isnearly depleted. Such signal is received by control system 13. Sensor 6and mirror 8 generate a feedback signal to control system 13 when an oldroll reduces in diameter sufficient that sensor 6 detects a reflectedback signal from mirror 8, corresponding with a diameter of the old webroll falling below a specific size. A time delay is then implemented bycontrol system 13, after which a splice is implemented automaticallycorresponding with a terminal end portion of the old web roll beingproximate splicer 10, ensuring a splice before the old web passesthrough splicer 10.

FIGS. 4-6 further illustrate construction of web splicing apparatus 10.In order to simplify the drawings, accumulator 11 has been omitted butis understood to be mounted atop apparatus 10 as depicted in FIGS. 1-3above. Optionally, accumulator 11 can be provided by a separatestand-along device. Apparatus 10 has a frame 12 that supports a controlbox 14, an entrance pre-feed assembly 16, an exit assembly 18 and asplice section assembly 20. A vacuum tank 22 for storing a source ofvacuum air is provided atop frame 12.

FIG. 6 illustrates pre-feed assembly 16 where a new sheet ofthermoformable material is received into the machine. The sheet is thenadvanced to the splice section assembly 20 where it is spliced togetherwith a trailing end of an old sheet of thermoformable material. Thesheet normally exits the machine via the exit assembly 18. Tank 22supplies an air vacuum from a vacuum source (not shown) for vacuum barsand clamp bars of the splice section assembly 20. The splice sectionassembly 20 includes an entrance vacuum bar assembly 130 and an exitvacuum bar assembly 132.

FIG. 7 shows an arrangement of coacting pre-feed wheels 24 (provided onboth lateral edges of an incoming sheet) driven by a pre-feed motor 28to drive a new sheet towards a nip/payout rollers assembly 26. Assembly26 is driven in coacting relation via a payout motor 30. Assembly 26 candrive new and old sheets in forward and reverse directions, undercomputer control. Motors 28 and 30 are computer driven servo motorscapable of being controlled by computer commands via control system 13(of FIG. 3).

According to one construction, prefeed motor 28 of FIG. 7 is a Siemensservo motor Model No. 1FK7043-7AK71-1DA3. Payout motor 30 of FIG. 7 is aSiemens servo motor Model No. 1FK7085-7AF71-1DA3. Furthermore, tiltmotor 32 (see FIG. 32) is a Siemens servo motor Model No.1FK7043-7AK71-1DA3 and splice align motor (for sheet thickness) 34 is aSiemens servo motor Model No. 1 FK7043-7AK71-1DA3. Finally, hot wiremotor 36 (see FIG. 36) is a Siemens servo motor Model No.1FK7043-7AK71-1DA3. These servo motors are available commercially in theUSA through Siemens Johnson City—SIAC, One Internet Plaza, Johnson City,Tenn. 37604, USA.

FIG. 8 illustrates the splice section assembly 20 from a side oppositeto that shown in FIG. 7. Further component details are shown in FIGS. 30and 31 below. More particularly, a tilt motor 32 drives a pair of splicetilt mechanisms 66 and 68 that are coupled together via a cross bar 70that links identical, but opposed articulating motions between the twomechanisms 66 and 68. A hot wire web cutting mechanism 38 supports anelectrically resistive heated hot wire between a pair of end spools forsevering and heating webs of thermoformable material that the wire isarticulated through via upward and downward pivotal motion of hot wireweb cutting mechanism 38. Hot wire web cutting mechanism 38 is driven upand down along a large arc via a hot wire motor 36. Further details ofhot wire web cutting mechanism 38 are shown below with reference to FIG.34. A splice alignment motor 34 adjusts one side of the splice sectionassembly 20 in elevational height as depicted below by FIG. 23.

FIG. 9 illustrates further details of the splice section assembly 20.More particularly, an upstream clamp assembly is formed by a servo bar40 and a clamp bar 42. A downstream clamp assembly is formed by a servobar 44 and a clamp bar 46. Bars 40, 42, 44 and 46 are each elongate,rectangular bars that have an internal vacuum manifold that feeds anarray of vacuum ports along respective bottom and top edges that contacta sheet of thermoformable material to hold the material. Vacuum barstiffener plates 48, 50, 52 and 54 support and stiffen bars 40, 42, 44and 46, respectively. A supply of vacuum is selectively applied andreleased to/from bars 40, 42, 44 and 46 in order to retain and release,respectively, a section of sheet during a splicing operation.

As shown in FIG. 9, a pair of lateral retraction assemblies 56 and 58are supported by frames 62 and 64, respectively, for laterallyretracting clamp bars 42 and 46 away from a splice line. Hence, clampbars 42 and 46 are designed to hold sheet scrap ends during a splicingoperation, and assemblies 56 and 58 each comprises a series of pneumaticcylinders 60 that retract and extend bars 42 and 46 during a splicingoperation.

FIG. 10 is a vertical sectional view of selected splicer sectioncomponents of splicer section assembly 20 corresponding with a sheetpayout mode where a terminating end of old thermoformable sheet 86 needsto be spliced onto a leading end of a new thermoformable sheet (notshown yet).

FIG. 11 is an enlarged view taken from the encircled region 11 of FIG.10 showing details of sheet 86 and the clamp bars and servo bars duringa sheet payout mode while thermoforming sheet 86, prior to running outof sheet 86. Splice tilt mechanisms 66 and 68 are shown coupled togetherfor motion via cross-bar 70. A tilt drive linkage, or crank 72 is drivenby the tilt motor (not shown) to drive eccentric links 74 and 76 to tilteach respective pair of servo bars and clamp bars about a respectivepivot point 78 and 80, respectively. The tilt causes movement toward andaway of webs captured by the servo and clamp bars relative to the otherset of servo and clamp bars. This can be used to urge together theheated seam on the old and new webs so as to push them together duringheating and fusing of the two edges.

Hot wire web cutting mechanism 38 includes a pair of arms that areclamped onto a pivot shaft in spaced apart relation. Each arm, at aradial end, supports a ceramic wheel with a conductive hot wirestretched between the wheels. The wire is raised and lowered to cutthrough sheets 86 and 88 and to heat severed ends of the sheets during asplicing operation, as described below. Mechanism 38 is driven inreciprocation by the hot wire motor. Optionally, a cutting wheel orblade (such as a carbide blade) can be provided on a linear track(supported by the frame) in order to cut the old and new sheets, andmechanism 38 can be used solely to heat and splice together the twosheets. For example, solid plastic sheet can be cut with a rotatingcutting wheel on a track, and mechanism 38 can be used to heat andsplice together the two sheets. This modification would overcome theneed for additional heat to quickly sever solid sheet, therebypotentially speeding up the operation.

FIG. 12 is a vertical sectional view of selected splicer sectioncomponents corresponding with a new sheet delivery mode. Moreparticularly, a leading end of a new sheet is overlapping old sheet 86prior to being spliced together. FIGS. 12 through 29 occur sequentially.

FIG. 13 is an enlarged view taken from the encircled region 13 of FIG.12 showing a leading end of new sheet 88 lying atop a trailing end ofold sheet 86. The hot wire 84 is provided below sheets 86 and 88.

FIG. 14 is a vertical sectional view of selected splicer sectioncomponents corresponding with a vacuum clamp mode where both servo barsand clamp bars are driven into engagement with sheets 86 and 88, and avacuum is applied to the sheets through vacuum ports in each bar 40, 42,44 and 46 from the vacuum tank 22 (see FIG. 4).

FIG. 15 is an enlarged view taken from the encircled region 15 of FIG.14 showing the bars contacting sheets 86 and 88 and application of avacuum to each from the respective bar.

FIG. 16 is a vertical sectional view of selected splicer sectioncomponents corresponding with a sheet apart mode. More particularly,servo motor 34 drives splice alignment mechanism 96 of FIG. 32 so as toarticulate splice section assembly 20 and move the sheets apartvertically in order to provide a gap between the sheets 86 and 88. Thegap prevents the hot, severed sheets from sticking with the adjacentscrap and adjacent sheet when the hot wire is driven through both sheets86 and 88.

FIG. 17 is an enlarged view taken from the encircled region 17 of FIG.16. Sheets 86 and 88 are separated prior to moving hot wire 84 upthrough the sheets, during the following step.

FIG. 18 is a vertical sectional view of selected splicer sectioncomponents corresponding with a wire cut sheets mode. Hot wire 84 hasbeen heated (by electrical resistance) and raised through sheets 86 and88, severing each sheet from adjacent scrap sheet.

FIG. 19 is an enlarged view taken from the encircled region 19 of FIG.18. A trailing scrap sheet 90 is severed from old sheet 86 and a leadingscrap sheet 92 is severed from a new sheet 88. Hot wire 84 has beenmoved to a raised position, above sheets 86 and 88, after severingsheets 86 and 88.

FIG. 20 is a vertical sectional view of selected splicer sectioncomponents corresponding with a scrap retract mode. The clamp bars andservo bars are holding each respective sheet via an applied vacuum whilethe respective pairs of servo bar and clamp bar are retracted laterallyaway from the other pair of servo bar and clamp bar.

FIG. 21 is an enlarged view taken from the encircled region 21 of FIG.20. The movement of clamp bars 42 and 46 moves the scrap sheets 92 and90, respectively, away (retracts) from the region to be spliced betweensheets 86 and 88.

FIG. 22 is a vertical sectional view of selected splicer sectioncomponents corresponding with a sheet alignment mode.

FIG. 23 is an enlarged view taken from the encircled region 23 of FIG.22. Servo bars 40 and 44 are driven down and up, respectively, to bringsheets 86 and 88 into alignment. Bars 46 and 42 are supported onpneumatic cylinders, so they follow the position of bars 40 and 44. Hotwire 84 is now centered between the severed ends of sheets 86 and 88where it applies heat to the severed edges.

FIG. 23A shows alignment of sheets 86 and 88 and positioning of wire 84.Splice alignment occurs using the mechanism of FIG. 33. Wire 84 is heldhere for a time (dwell delay that can be adjusted, depending on thesheet. Computer control via processing circuitry, memory and a programenables tailoring of the dwell time where motion is held still duringthe heating process.

FIG. 24 is a vertical sectional view of selected splicer sectioncomponents corresponding with a sheet approach mode. During this stage,the heated wire dwell ends and the sheets 86 and 88 are moved closertogether (using the splice tilt mechanism of FIG. 32).

FIGS. 25 and 25A provide enlarged views taken from the encircled region25 of FIG. 24 and the encircled region 25A of FIG. 25, respectively.Sheets are brought closer together during heating by wire 84 as eachclamp assembly is tilted so as to push the edges of sheets 86 and 88closer together. During this step, wire 84 “dwells” between the edges ofsheets 86 and 88, delivering heat thereto and generating a melted bead.FIG. 25B is taken later in time than the view of FIGS. 25 and 25A anddepicts the further advancement together of the edges of sheet, buildinga melted bead or pool on each edge. During a “mashing” operation, it ispresently believed (although not certain) that the melted beads on eachedge intermix and join together to form a stronger splice because of thepresence of the beads and the increased rate with which the “mash”operation of FIG. 27B is implemented. It is presently believed that thecreation of these melted beads is somewhat analogous to formation of awelding bead when welding steel. The building of this bead in the stepsof FIGS. 25A and 25B has been found through preliminary testing togenerate a stronger and less brittle splice. The trailing terminal edgeand the leading terminal edge are both heated with the heating element,or wire, sufficiently to impart melt-back of each edge away from theheating element at a melt-back rate. While heating the leading terminaledge and the trailing terminal edge, the leading terminal edge and thetrailing terminal edge are each moved towards the heating element at arate no greater than the melt-back rate so as to prevent contact of eachedge with the heating element while maintaining proximity with theheating element to deliver heat to each edge. Additionally, the processthat forms the bead edge on each sheet also straightens out the edge,eliminating any “mouth-shaped edge” caused during severing and resultingfrom sheet stresses.

FIG. 26 is a vertical sectional view of selected splicer sectioncomponents corresponding with a wire withdraw and sheet load mode.During this mode, the wire is moved down and the sheets 86 and 88 arebrought even closer together, pushing the heated edges together andfusing them into a single sheet with a splice 85 (see FIG. 29).

FIG. 27 is an enlarged view taken from the encircled region 27 of FIG.26. Sheets 86 and 88 and being fused together by pressure and heat. FIG.27A shows the ends of sheets 86 and 88 fusing together as servo bars 40and 44 are rotated further together.

FIG. 27B occurs later in time than FIG. 27A and depicts a “mash” stepwhere the heated ends of sheet are pushed together edge-wise at a higherrate (than in FIG. 25B), imparting greater fusing and increased strengthand resilience to the resulting joining splice. As shown in FIGS. 25Aand 25B, while heating the leading terminal edge and the trailingterminal edge, the leading terminal edge and the trailing terminal edgeeach move towards the heating element at a rate no greater than themelt-back rate so as to prevent contact of each edge with the heatingelement while maintaining proximity with the heating element to deliverheat to each edge. In the step of FIG. 27B, the rate with which theleading terminal edge and the trailing terminal edge are moved togetheris increased in order to fuse together the leading terminal edge and thetrailing terminal edge as they cool to form a connection seam.

FIG. 28 is a vertical sectional view of selected splicer sectioncomponents corresponding with a sheet apart and scrap withdrawal mode.During this mode, the fused together sheets 86 and 88 are run in reversedirection from the sheet flow direction, perhaps for several feet. Scrap90 is ejected and dropped while a vacuum still holds scrap 92 for laterremoval by a machine operator or technician.

FIG. 29 is an enlarged view taken from the encircled region 29 of FIG.28. Fused together sheets 86 and 88 are being advanced to show splice85. This splice operation occurs quick enough that a continuous sheet86/88 can be spliced together to feed a continuously operatingthermoforming operation without having to stop and start thethermoforming machine.

In one exemplary implementation, tests were run using polystyrene foamsheet with 8.5 pound density and 0.1″ (one hundred thousandth inch)thickness. A one (1) millimeter diameter Inconel® X750 hot wire washeated to 800 degrees Fahrenheit (a range of 700 to about 1200 degreesFahrenheit has been found to work for various materials). A melt-backdistance (see FIGS. 25A and 25B) on each sheet of 0.115″ inches wasachieved and a 0.025″ “mash” distance was achieved on each sheet. It wasfound through preliminary testing that any delays greater than 200milliseconds from the time heat was removed from the sheet edges and thetime that “mash” initiated resulted in a non-desirable weakening instrength and resilience of the resulting splice. It is presentlybelieved that air quickly cools a surface along each melted bead on eachsheet edge, and the “mash” step of FIG. 27B (occurring at a higherspeed) better intermixes the internal melted regions of each meltedbead, thereby resulting in a stronger splice.

FIG. 30 is a component perspective view of the entrance vacuum barassembly 130 shown in FIGS. 6 and 9. Assembly 130 is formed by an uppervacuum bar stiffener plate 48 that is mounted for reciprocation inparallel relation relative to a lower vacuum bar stiffener plate 50 viaa pair of parallel die post assemblies 144 and 145. A pair of tiltlinkages 228 and 229 on splice alignment mechanism 96 (see FIG. 34)attach via pivotally supported and threaded attachment bolts 212 and213, respectively, in threaded engagement with sheet thickness mounts116 and 117 to a top end of plate 48 in order to adjust verticalpositioning of plate 48 during a splicing operation. A pair of togglebrackets 236 and 237 on splice alignment mechanism 96 (see FIG. 34)attach via pivotally supported and threaded attachment bolts 210 and211, respectively, in threaded engagement with clamping drive mounts 108and 110 to a bottom end of plate 50 in order to adjust verticalpositioning of plate 50 during a splicing operation. Furthermore, a pairof eccentric cam linkages 256 and 257 on splice tilt mechanism 94 (seeFIG. 35) attach via pivotally supported and threaded attachment bolts220 and 221, respectively, to cam mounts 112 and 113 along a bottom edgeof plate 50 in order to tilt the assembly of plates 48 and 50 toward andaway from the assembly of plates 52 and 54 when delivering severed endsof an old web and a new web toward a heating wire during a heatingoperation, as well as when driving together the heated ends during afusing, or mash operation (see FIGS. 25-27). Each bolt 220 and 221passes through a cylindrical cam spacer 114 and 115, respectively,before threading into respective mount 112 and 113.

Plate 48 is supported for up and down reciprocation atop plate 50 viadie post assemblies 144 and 145, as shown in FIG. 30. Assemblies 144 and145 are each respectively formed from a double rod pneumatic cylinder138 and 140 that is mounted at both ends of a cylinder mount basebracket 146 and 147, respectively. One suitable cylinder 138, 139 is anSMC Model No. NCDGWBA50, High Speed/Precision Cylinder, Double Acting,Single Rod, pneumatic cylinder sold by SMC Corp of America, USHeadquarters, 10100 SMC Blvd., Noblesville, Ind. 46060. No pneumaticfluid is delivered to each cylinder. Instead, pneumatic supply fittingsat opposed ends of each cylinder are joined together with a pneumatictube in order to prevent contaminants from entering each cylinder. Acentral body of each cylinder 138 and 140 is secured onto plate 48 via acylindrical clamp assembly 118 and 119, respectively. A vacuum bar endclamp, such as clamp 120, secures each end of vacuum bar 40 onto thecentral body of each cylinder 138 and 140. Die post assemblies 144 and145 are constructed in a manner similar to die post assemblies 142 and143, described in greater detail below with reference to FIG. 31.

Servo bar 40 and clamp bar 42 of FIG. 30 each receive a vacuum via aplurality of flexible vacuum tubes 106 and 107. Tubes 106 and 107 arefluidly coupled to common vacuum manifolds 102 and 103, respectively,that receive a vacuum source via main vacuum lines 104 and 105. Suchvacuum is selectively applied and removed during a splicing operationwhen necessary to retain and release a section of thermoformable webmaterial.

Clamp bar 42 is supported by a plurality of double acting, double rodpneumatic cylinders 60, as shown in FIG. 30. Each cylinder 60 is mountedat each rod end to plate 50 and a cylinder attachment bar 159 that issecured onto plate 50 via a cylinder mounting bar 158. A body of eachcylinder is secured with threaded fasteners onto a bottom surface ofclamp bar 42. One suitable cylinder 60 is an SMC Model No. SMC MUWB50-25D, plate cylinder, double acting, double rod, pneumatic cylindersold by SMC Corp of America, US Headquarters, 10100 SMC Blvd.,Noblesville, Ind. 46060. A cylindrical plastic bumper 160 is provided onone rod of each cylinder 60 away from bar 42 to limit lateral movementto a predetermined amount. A pneumatic manifold 122 supplies pressurizedair, or pneumatic fluid via fluid lines to each actuator 60.

FIG. 31 is a component perspective view of the exit vacuum bar assembly132 shown in FIGS. 6 and 9. Assembly 132 is formed by an upper vacuumbar stiffener plate 48 that is mounted for reciprocation in parallelrelation relative to a lower vacuum bar stiffener plate 50 via a pair ofparallel die post assemblies 142 and 143. A pair of tilt linkages 232and 233 on splice alignment mechanism 96 (see FIG. 34) attach viapivotally supported and threaded attachment bolts 216 and 217,respectively, in threaded engagement with sheet thickness mounts 176 and177 to a bottom end of plate 52 in order to adjust vertical positioningof plate 52 during a splicing operation. A tilt spacer bushing 180 isprovided in each mount 176 and 177 (see FIG. 6). A pair of togglebrackets 238 and 239 on splice alignment mechanism 96 (see FIG. 34)attach via pivotally supported and threaded attachment bolts 214 and215, respectively, in threaded engagement with clamping drive mounts 170and 172 to a top end of plate 54 in order to adjust vertical positioningof plate 54 during a splicing operation. Furthermore, a pair ofeccentric cam linkages 258 and 259 on splice tilt mechanism 94 (see FIG.35) attach via pivotally supported and threaded attachment bolts 222 and223, respectively, to cam mounts 174 and 175 along a top edge of plate54 in order to tilt the assembly of plates 52 and 54 toward and awayfrom the assembly of plates 48 and 50 when delivering severed ends of anold web and a new web toward a heating wire during a heating operation,as well as when driving together the heated ends during a fusing, ormash operation (see FIGS. 25-27). Each bolt 222 and 223 passes through acylindrical cam spacer bushing 178 and 179, respectively, beforethreading into respective mount 174 and 175.

Plate 52 is supported for up and down reciprocation beneath plate 54 viadie post assemblies 142 and 143, as shown in FIG. 31. Assemblies 142 and143 are each respectively formed from a double rod pneumatic cylinder134 and 136 that is mounted at both ends of a cylinder mount basebracket 146 and 147, respectively. One suitable cylinder 134, 136 is anSMC Model No. NCDGWBA50, High Speed/Precision Cylinder, Double Acting,Single Rod, pneumatic cylinder sold by SMC Corp of America, USHeadquarters, 10100 SMC Blvd., Noblesville, Ind. 46060. No pneumaticfluid is delivered to each cylinder. Instead, pneumatic supply fittingsat opposed ends of each cylinder are joined together with a pneumatictube in order to prevent contaminants from entering each cylinder. Acentral body of each cylinder 134 and 136 is secured onto plate 44 via acylindrical clamp assembly 154 and 155, respectively. A vacuum bar endclamp, such as clamp 152, secures each end of vacuum bar 40 onto thecentral body of each cylinder 134 and 136. Die post assemblies 142 and143 are constructed in a manner similar to die post assemblies 138 and140, described in greater detail above with reference to FIG. 30.

Servo bar 44 and clamp bar 46 of FIG. 31 each receive a vacuum via aplurality of flexible vacuum tubes 166 and 167. Tubes 166 and 167 arefluidly coupled to common vacuum manifolds 162 and 163, respectively,that receive a vacuum source via main vacuum lines 164 and 165. Suchvacuum is selectively applied and removed during a splicing operationwhen necessary to retain and release a section of thermoformable webmaterial.

Clamp bar 46 is supported by a plurality of double acting, double rodpneumatic cylinders 60, as shown in FIG. 31. Each cylinder 60 is mountedat each rod end to plate 54 and a cylinder attachment bar 159 that issecured onto plate 54 via a cylinder mounting bar 158. A body of eachcylinder is secured with threaded fasteners onto a top surface of clampbar 46. One suitable cylinder 60 is an SMC Model No. SMC MUWB 50-25D,plate cylinder, double acting, double rod, pneumatic cylinder sold bySMC Corp of America, US Headquarters, 10100 SMC Blvd., Noblesville, Ind.46060. A cylindrical plastic bumper 160 is provided on one rod of eachcylinder 60 away from bar 46 to limit lateral movement to apredetermined amount. A pneumatic manifold 168 supplies pressurized air,or pneumatic fluid via fluid lines to each actuator 60.

FIG. 32 is a component perspective view of the splice section assembly20 of FIG. 8 taken from the same end of the machine. A lateral scrapretraction assembly 56 is shown with a plurality of spaced-apartpneumatic cylinders 60 (see FIG. 9) used to laterally retract clamp bar42, as shown in FIG. 21. Splice section assembly 20 includes entrancevacuum bar assembly 130 and exit vacuum bar assembly 132 which arearticulated to desirable positions using the kinematic mechanismsdescribed below with reference to FIGS. 34 and 35.

FIG. 33 is a component perspective view of the splice section assemblyof FIGS. 8 and 32 taken from an opposite end of the machine and showinglateral scrap retraction assembly 58 used to laterally retract clamp bar46, as shown in FIG. 21. Interconnecting cross members 70 and 71 areprovided in order to couple together the kinematic motions of entrancevacuum bar assembly 130 and exit vacuum bar assembly 132.

FIG. 34 is a component perspective view of the splice alignmentmechanism 96 taken from the same end as FIG. 33. Splice alignmentmechanism 96 articulates entrance vacuum bar assembly 130 (see FIG. 30)and exit vacuum bar assembly 132 (see FIG. 32) so as to perform thevertical alignment between sheets 86 and 88, as shown in FIGS. 22 and23. More particularly, servo motor 34 drives splice alignment mechanism96 back and forth via primary crank arm 248 and a secondary crank arm249, as shown in FIGS. 34 and 35. Crank arm 249 pivots shaft 205 backand forth so as to pivot tilt linkages 232 and 233 up and down, whichraises and lowers fasteners 216 and 217, respectively.

As shown in FIG. 34, a compound crank arm 250 is affixed onto an end ofshaft 205 in order to drive remaining shafts 202-204 in correspondingpivotal motion. Shafts 202-205 are each mounted at each end to opposedwalls on frame 12 with rotary bearing assemblies. A drive linkage 246 ispivotally affixed via a bearing mount onto crank arm 250 and via asecond bearing mount onto a driven crank arm 255. Crank arm 255 isaffixed onto an end of shaft 202 to drive tilt linkages 226 and 227 incorresponding up and down motion. A pair of toggle brackets 236 and 237are pivotally coupled with bearing mounts onto tilt linkages 226 and227, respectively. Fasteners 210 and 211 are each mounted with bearingmounts onto top ends of each respective toggle bracket 236 and 237,Drive linkage 246 includes a pneumatic cylinder 243 that is pressurizedduring use so as to provide a spring within linkage 246. One suitablepneumatic cylinder 243 is an SMC Model No. NCG50-ICN004-0100, SMC NCGCYLINDER 50mM BORE 1″ STROKE W/AIR CUSHION & 5/8-11 THREAD, pneumaticcylinder sold by SMC Corp of America, US Headquarters, 10100 SMC Blvd.,Noblesville, Ind. 46060. Likewise, another drive linkage 244 ispivotally affixed via a bearing mount onto crank arm 250 and via asecond bearing mount onto a driven crank arm 252. Crank arm 252 isaffixed onto an end of shaft 204 to drive tilt linkages 230 and 231 incorresponding up and down motion. A pair of toggle brackets 238 and 239is pivotally coupled with bearing mounts onto tilt linkages 230 and 231,respectively. Fasteners 214 and 215 are each mounted with bearing mountsonto bottom ends of each respective toggle bracket 238 and 239. Drivelinkage 244 includes a pneumatic cylinder 242 that is pressurized duringuse so as to provide a spring within linkage 244. One suitable pneumaticcylinder 242 is an SMC Model No. NCG50-ICN004-0100, SMC NCG CYLINDER 50mM BORE 1″ STROKE W/AIR CUSHION & 5/8-11 THREAD, pneumatic cylinder soldby SMC Corp of America, US Headquarters, 10100 SMC Blvd., Noblesville,Ind. 46060. Finally, a drive linkage 71 is pivotally affixed via abearing mount onto crank arm 250 and via a second bearing mount onto adriven crank arm 254. Crank arm 254 is affixed onto an end of shaft 203to drive tilt linkages 228 and 229 in corresponding up and down motion.Tilt linkages 228 and 229 drive fasteners 212 and 213, respectively, upand down.

FIG. 35 is a component perspective view of the splice tilt mechanism 94taken from the same end as FIG. 32. This mechanism 94 tilts or pivotsthe bars in order to drive together sheets 86 and 88, as shown in FIGS.23-27B. Splice tilt mechanism 94 articulates entrance vacuum barassembly 130 (see FIG. 30) and exit vacuum bar assembly 132 (see FIG.32) so as to move together ends of sheets 86 and 88 during the steps ofFIGS. 24-26, as well as during the “mash” operation of FIGS. 26-27. Moreparticularly, shaft 207 supports a pair of eccentric cam bearingassemblies 260 provided in eccentric cam linkages 258 and 259. Likewise,shaft 206 supports a pair of eccentric cam bearing assemblies 260provided in eccentric cam linkages 256 and 257. Each cam bearingassembly is formed by machining an offset axis cylindrical outer surfacethat is offset from the center of axis of the respective shaft. Acrescent moon shaped segment that complements the outer surface combinesto fill in the inner cylindrical surface of an inner bearing race of thecam bearing assembly 260. Alternatively, a cylindrical end segment ofeach shaft 206 and 207 can be cut off and welded onto a respective endof the shaft so as to create a cylindrical segment with a center axisoffset from the center axis of the respective shaft. Other techniquesfor forming an eccentric cam bearing assembly can also be used so as toconvert rotational motion of each shaft into laterally reciprocatingmotion of each eccentric cam linkage 256-259. Bearing supported bolts220-223 mount into respective cam mounts 114, 115 (see FIG. 30) and 174,175 (see FIG. 31) so that splice tilt mechanism drives entrance vacuumbar assembly 130 (see FIG. 30) and exit vacuum bar assembly 132 (seeFIG. 31). Tilt motor 32 drives eccentric cam linkages 256-259substantially horizontally to and fro by rotating shafts 206 and 207through rotatable coupling of crossbar 70 and coupled crank arms 272 and273. Tilt motor 32 drives shaft 206 in back and forth rotation viaprimary crank arm 270 and secondary crank arm 271.

FIG. 36 illustrates one implementation for a web cutting apparatuscomprising a hot wire web cutting mechanism 38. Optionally, a blade orscissor cutting mechanism can be used to cut a terminal end of an oldweb and a leading end of a new web prior to splicing them together. Moreparticularly, web cutting mechanism 38 comprises a hot wire 84 carriedunder tension between a pair of wheels 79 and 82. Wheels 79 and 82 eachreceive wire 84 is a circumferential outer groove. Wheel 82 is pivotallysupported by an arm 262 (with a bearing) and includes an integral armrotates wheel 82 so as to tension wire 84 as a result of a tensionedcoil spring 267. Wheel 79 is rigidly mounted on arm 263. Arms 262 and263 are rigidly secured on opposite ends of a cylindrical shaft 208. Adrive arm 264 secures onto shaft 208 and drives shaft 208 into rotationin order to raise and lower wire 84. Shaft 208 is supported at each endwith a rotational bearing supported by end plates of the frame 12 forapparatus 10 (see FIG. 1). A crank arm 264 drives arm 264 and shaft 208in response to activation of a hot wire servo drive motor 36. Aelectromagnetic sensor 268 detects position of motor 36 base uponmovement of a base plate on motor 36.

FIG. 37 is a logic flow diagram illustrating the steps implemented bythe control system when setting up and performing a splice between atrailing end of an old, or first web and a leading end of a new, orsecond web.

In Step “S1”, a thermoforming machine, web splicer and web accumulatorare provided along with a source of thermoformable web comprising an oldweb and a new web to be spliced onto the old web. The web accumulatorhas an articulating frame and a height adjustable roller provided alonga downstream end of the splicer. A control system is also provided alongwith an actuator that is controlled to articulate the frame so as toraise and lower the roller when accumulating extra web and releasing theaccumulated web when splicing the new web onto the old web so that adownstream thermoforming machine can run at a consistent cyclical rate,even during a splicing operation. After performing Step “51”, theprocess proceeds to Step “S2”.

In Step “S2”, an operator determines a cycle time for the operatingthermoforming machine for a specific thermoformable web and a specificdie set. After performing Step “S2”, the process proceeds to Step “S3”.

In Step “S3”, an operator determines a shot length for the operatingthermoforming machine for a specific thermoformable web and a specificdie set. After performing Step “S3”, the process proceeds to Step “S4”.

In Step “S4”, an operator sets a splice cycle time for the web splicer.After performing Step “S4”, the process proceeds to Step “S5”.

In Step “S5”, an operator determines a minimum length of surplus webneeded by the thermoforming machine during a splice cycle time. Afterperforming Step “S5” the process proceeds to Step “S6”.

In Step “S6”, a control system drives the splicer to deliver the old webthrough the splicer and to an operating thermoforming machine toaccumulate at least the minimum length of web, or sheet. Concurrent withor after performing Step “S6”, the process proceeds to Step “S7”.

In Step “S7”, an operator arms the splicer to automatically perform asplice in response to a web terminal end condition being detected forthe old web. In one case, a preselected time delay is provided betweendetecting the condition and performing the splice. In another case, thesplice occurs immediately after detecting the condition. Afterperforming Step “S7”, the process proceeds to Step “S8”.

In Step “S8”, the control system detects with a sensor presence of aterminal end condition for the old web. If a terminal end condition isdetected, the process proceeds to Step “S9”. If not, the process returnsto Step “S8”.

In Step “S9”, the control system drives the actuator to raise theaccumulator roller sufficient to accumulate a length of surplus webneeded for use when splicing a leading end of a new web to a terminalend of the old web. After performing Step “S9”, the process proceeds toStep “S10”.

In Step “S10”, the control system drives the actuator to lower theaccumulator roller sufficient to supply the accumulated length ofsurplus web for use by the thermoforming machine while splicing the oldweb to the new web. After performing Step “S10”, the process proceeds toStep “S11”.

In Step “S11”, the new web becomes an old web and a subsequent new webis provided to the splicer. After performing Step “S11”, the processproceeds to Step “S7”. If a new web is not provided, the process isterminated.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method for joining together thermoformable sheets, comprising: providing a first thermoformable sheet overlapped with a second thermoformable sheet; moving a heating element through the first sheet and the second sheet to form a trailing terminal edge and a leading terminal edge, respectively; aligning in proximate, spaced-apart relation the trailing terminal edge and the leading terminal edge; inserting the heating element between and spaced from the trailing terminal edge and the leading terminal edge; while holding the heating element between the trailing terminal edge and the leading terminal edge, heating the trailing terminal edge and the leading terminal edge with the heating element sufficiently to impart melt-back of each edge away from the heating element at a melt-back rate; while heating the leading terminal edge and the trailing terminal edge, moving the leading terminal edge and the trailing terminal edge each towards the heating element at a rate no greater than the melt-back rate so as to prevent contact of each edge with the heating element while maintaining proximity with the heating element to deliver heat to each edge; removing the heating element from between the trailing terminal edge and the leading terminal edge; and after removing, fusing together the leading terminal edge and the trailing terminal edge by moving together the leading terminal edge and the trailing terminal edge until respective melted portions on each edge engage.
 2. The method of claim 1, wherein the heating element comprises a tensioned wire heated through electrical resistance.
 3. The method of claim 1, wherein moving the heating element comprises melting a path through the sheets with the heating element as the heating element is passed through the sheets.
 4. The method of claim 1, further comprising, after moving the edges to engage, increasing the rate with which the leading terminal edge and the trailing terminal edge move together to fuse together the leading terminal edge and the trailing terminal edge as they cool to form a connection seam.
 5. The method of claim 1, wherein moving a heating element through the first sheet and the second sheet forms a first scrap sheet and a second scrap sheet.
 6. The method of claim 1, further comprising retaining the first scrap sheet and the second scrap sheet.
 7. The method of claim 6, further comprising moving the first scrap sheet and the second scrap sheet away from a splice location between the leading terminal edge and the trailing terminal edge.
 8. The method of claim 1, further comprising holding the first scrap sheet and the second scrap sheet away from the splice location while fusing together the leading terminal edge and the trailing terminal edge.
 9. A method for joining together thermoformable sheets, comprising: providing a first thermoformable sheet with a trailing terminal edge and a second thermoformable sheet with a leading terminal edge; aligning in proximate, spaced-apart relation the trailing terminal edge and the leading terminal edge; inserting a heating element between and spaced from the trailing terminal edge and the leading terminal edge; while holding the heating element between the trailing terminal edge and the leading terminal edge, heating the trailing terminal edge and the leading terminal edge with the heating element sufficiently to impart melt-back of each edge away from the heating element at a melt-back rate; while heating the leading terminal edge and the trailing terminal edge, moving the leading terminal edge and the trailing terminal edge each towards the heating element at a rate no greater than the melt-back rate so as to prevent contact of each edge with the heating element while maintaining proximity with the heating element to deliver heat to each edge; removing the heating element from between the trailing terminal edge and the leading terminal edge; and after removing, moving the leading terminal edge and the trailing terminal edge together until respective melted portions on each edge engage.
 10. The method of claim 9, further comprising, after moving the edges to engage, increasing the rate with which the leading terminal edge and the trailing terminal edge move together to fuse together the leading terminal edge and the trailing terminal edge as they cool to form a connection seam.
 11. The method of claim 9, prior to aligning, moving the heating element through the first sheet and the second sheet to form a trailing terminal edge and a leading terminal edge, respectively.
 12. The method of claim 9, wherein moving the heating element forms a first scrap sheet and a second scrap sheet.
 13. The method of claim 12, further comprising retaining the first scrap and the second scrap after severing from the first thermoformable sheet and the second thermoformable sheet.
 14. The method of claim 13, further comprising moving the retained first scrap and the second scrap away from a splice zone between the leading terminal edge and the trailing terminal edge.
 15. The method of claim 9, wherein moving together the leading terminal edge and the trailing terminal edge comprises butt-welding together the respective melted portions.
 16. An apparatus for joining together thermoformable sheets, comprising: a frame; an entrance vacuum clamping bar assembly supported by the frame and having a vacuum clamping member supported for movement toward and away for a vacuum servo member generally perpendicular to a sheet travel path, the vacuum clamping member further supported for retraction and extension parallel to the sheet travel path; an exit vacuum clamping bar assembly supported by the frame downstream of the entrance vacuum clamping bar assembly and having a clamping member supported for movement toward and away from a vacuum servo member generally perpendicular to a sheet travel path, the vacuum clamping member further supported for retraction and extension parallel to the sheet travel path; a sheet severing mechanism for severing an overlapped old sheet and new sheet; and at least one actuator carried by the frame and configured to move each of the vacuum clamping members toward and away from a splice to retract scrap sheet away from a splice line between the entrance vacuum clamping bar assembly and the exit vacuum clamping bar assembly; wherein one of the entrance and exit vacuum clamping member is provided above the respective vacuum servo member and another of the entrance and exit vacuum clamping member is provided below the respective vacuum servo member.
 17. The apparatus of claim 16, further comprising an actuator coupled with the entrance vacuum clamping bar assembly and configured to move the entrance vacuum clamping bar assembly toward and away from the exit vacuum clamping bar assembly.
 18. The apparatus of claim 16, further comprising an actuator coupled with the exit vacuum clamping bar assembly toward and away from the entrance vacuum clamping bar assembly.
 19. The apparatus of claim 16, further comprising a tilt mechanism coupled with the entrance vacuum clamping bar assembly and the exit vacuum clamping bar assembly and configured to tilt the entrance vacuum clamping bar assembly and the exit vacuum clamping bar assembly toward and away from one another.
 20. The apparatus of claim 16, further comprising a sheet adjust mechanism coupled with the entrance vacuum clamping bar assembly and the exit vacuum clamping bar assembly and configured to reposition one of the vacuum servo members relative to the other of the vacuum servo motors to align an old sheet and a new sheet prior to heating and butt-welding together.
 21. The apparatus of claim 16, wherein the sheet severing mechanism comprises a hot wire.
 22. The apparatus of claim 21, wherein each vacuum clamping member is retracted from a respective vacuum servo member while applying a vacuum to separate the old sheet from the new sheet while the hot wire is moved through the old sheet and the new sheet during a sheet severing operation.
 23. The apparatus of claim 21, wherein the at least one actuator laterally retracts each vacuum clamping member away from a splice line for clearance during a splicing operation. 